Given the increase in the number of users of two-wheeled vehicles and the number of serious accidents, the need to protect the motorcyclist in case of an accident has become a major concern. The compulsory wearing of a helmet in some countries has been one of the main decisions taken in this direction. However, progress can still be made.
Having seen the benefit of airbag protection in the automotive field, it has been sought to design and develop an equivalent device suitable to be worn by a person, and therefore in particular by the driver of a two-wheeled vehicle.
Various devices have been the subject of patent applications. Mention will be made by way of example of British patent GB 1 524 022, dating from 1974, which describes such a device for protection of a person, comprising an airbag. The inflation is provided by a single stage pyrotechnic gas generator, activated by a radio signal. Mention may also be made of European patent EP043990, which describes a protective device which is inflated by a cartridge of compressed gas, activated by breaking a wire link.
At the present time, some devices are marketed. They are of the type described in patent application EP043990 mentioned above, and may be characterized by the presence of an inflatable structure, of a small reservoir of pressurized gas whose opening makes it possible to inflate the inflatable structure, and of a wire connecting the motorcyclist to the motorbike and which activates the inflation when the motorcyclist is subject to a tensile force.
Several remarks, are called for. The devices currently on the market may be improved in terms of energy absorption without rebound. Furthermore, the inflation by opening a small reservoir of pressurized gas has four major drawbacks:                the period of time for inflating the protective structure is high with respect to the speed with which the accident occurs and any contact of the motorcyclist with obstacles,        the volume of the reservoir and of its activation system is high,        the hardness of this reservoir may cause significant injuries even in the case of minor accidents,        the continuous presence, throughout the equipment life, of this high-pressure reservoir against the body is not very reassuring.        
Another drawback of the devices currently marketed is that the activation by tensile force on a wire is not desired by the motorcyclists, because it causes inadvertent operation of the device should the motorcyclist fall on stopping, or at low speed, or should the motorcyclist forget to disconnect the device when getting off the motorcycle.
Moreover, the pyrotechnic gas generators do not allow the airbag to be maintained under pressure during the several seconds needed to respond to the various accidental situations. This is because, under the effect of the rapid reduction in temperature of the gas after inflation, the pressure in the airbag decreases. Analyses of accidents show that it is necessary to inflate the protective structure very fast, 50 ms at most, then to maintain this inflated structure for several seconds. Fast inflation which is not maintained is not effective enough to allow the safety device to fulfil its role completely.
Thus, in spite of considerable research carried out in this field, and of the development of a certain number of devices containing an airbag, for more than twenty years, there remains a need for a protective device comprising an airbag worn by an individual, with both fast and maintained inflation. The Applicants have succeeded in developing such a device.